Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 270848
SWOD48
SPC AC 270846

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0346 AM CDT SAT AUG 27 2016

VALID 301200Z - 041200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS INCLUDING THE ECMWF AND GFS BEGIN THE DAY 4
TO 8 PERIOD WITH AN UPPER-LEVEL RIDGE IN THE NRN HIGH PLAINS AND
WEST TO NORTHWEST MID-LEVEL FLOW FROM THE NRN PLAINS ESEWD ACROSS
THE GREAT LAKES INTO THE NERN STATES. THE MODELS MOVE THE
UPPER-LEVEL RIDGE SLOWLY EWD ACROSS THE NCNTRL U.S. FROM TUESDAY/DAY
4 TO THURSDAY/DAY 6. A PERSISTENT AXIS OF INSTABILITY IS FORECAST
BENEATH THE UPPER-LEVEL RIDGE ACROSS THE GREAT PLAINS DURING THAT
TIME. ISOLATED THUNDERSTORMS MAY DEVELOP EACH AFTERNOON AND EVENING
DURING THE MIDDLE OF THE WEEK BUT THE PRESENCE OF THE UPPER-LEVEL
RIDGE SHOULD BE A LIMITING FACTOR FOR SEVERE.

ON FRIDAY/DAY 7 AND SATURDAY/DAY 8...BOTH THE ECMWF AND GFS FORECAST
SOUTHWEST MID-LEVEL FLOW TO BECOME ESTABLISHED ACROSS THE NCNTRL
STATES IN THE WAKE OF THE UPPER-LEVEL RIDGE. IF THIS OCCURS LATE IN
THE WEEK...INCREASING LARGE-SCALE ASCENT AND STRONGER DEEP-LAYER
SHEAR IN THE NRN PLAINS AND UPPER MS VALLEY COULD RESULT IN A CHANCE
FOR STRONG TO SEVERE THUNDERSTORMS LATE FRIDAY AFTERNOON AND LATE
SATURDAY AFTERNOON. HOWEVER...THE ECMWF AND GFS SOLUTIONS ARE NOT IN
AGREEMENT CONCERNING THE FINER-SCALE DETAILS LATE IN THE WEEK ACROSS
MUCH OF THE CONUS SUGGESTING PREDICTABILITY REMAINS LOW.

..BROYLES.. 08/27/2016



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